When dealing with cards, there is something you have to look at before sending them out to be signed... you have to look at the surface of the card. Modern cards tend to have a high gloss on them, and that looks wonderful, but it is horrible for autographs. The ink from pens like Sharpies will not adhere to a glossy surface, and will just bead up and rub off. Prior to about 1995, collectors didn't need to worry about this. Glossy surfaces were not widely used and ink would adhere just fine. But all is not lost. You can still use glossy cards for autographs, it just takes some preparation.
|Image courtesy of martcollectables123 on Ebay|
There are two methods of 'preping' cards. One is by using an eraser, the gum or rubber type, and gently rub the eraser across the surface of the card. I have tested this method on a few cards and had mixed results. This method can also leaves a milky film on the card.
The other method, the one I use, is with baby powder. Simply put a small amount of the powder onto the card and rub the surface with it. The tack in the baby powder will allow the surface to take the ink. Just make sure to rub down the entire surface, you never know where the person will sign the card. Than just wipe off the remaining powder and it is ready for the mailbox.
Here is a link to a wonderful video by 'theautographnetwork' on YouTube showing both methods. Check it out.
May your mailbox be filled with autographs and not bills!